Many arteriovenous fistulas (AVFs) suffer thrombosis or fail to mature and become usable. The Univ. of Utah will participate as a Clinical Center to conduct a prospective multi-center observational cohort study, investigating factors associated with the failure of AVF to mature. Major hypotheses are:(1) The usability of native AVF in CKD and dialysis patients can be predicted by a number of pre-, peri- and post-operative factors. (2) Defining these factors will allow the development of algorithms that are superior to physical examination alone in predicting AVF usability. (3) The blood flow rate and depth of the AVF determined by ultrasound at certain post-placement time points can serve as a surrogate for the usability of AVF. Specific Aims are to: (1) determine the pre-, peri- and post-operative local and/or systemic factors associated with AVF failure and the prevalence of these factors; (2) identify and evaluate intermediate outcomes as potential surrogates for AVF usability; (3) participate in the design and execution of the multi-center study. Other Aims are to: (4) determine the medical complications associated with the unusable AVF; (5) propose as ancillary studies the values of very early (3-hr) ultrasound results, plasma inflammation markers and novel platelet markers as predictors of AVF failure. Strengths of this application are: (1) a dedicated, multi-disciplinary team of researchers, with experience in clinical care of dialysis patients and AVF, and in clinical and laboratory research related to vascular access and kidney diseases; (2) a sizable independent academic dialysis program under the direction of the PI that would ensure maximum cooperation from the dialysis staff; (3) as Co-investigators, a surgical team that integrates vascular surgery with interventional radiology, vascular diagnostic tests and research; (4) integration of clinical and laboratory research that should facilitate the exploration of novel biological principles and therapies. Successful development of a prediction algorithm for AVF failure will help to guide the clinical practice of whether, when and how to place, monitor and/or implement corrective actions for the AVF. Identification of risk factors for usability failure and establishment of an objective biological surrogate for usability would facilitate the design of interventional trials targeting modifiable factors. Further, the pursuit of novel factors may promote the understanding of the pathogenesis of AVF failure that could potentially lead to new therapeutic strategies.